Block-signal system.



L. A. HAWKINS.

. BLOCK SIGNAL SYSTEM.

APPLICATION FILED APR. 23.1909.

937,440. Patented Oct. 19,1909,

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. power-current from one block to the next-so I the power-current, ,while confining the signal bonds which,if the power current is large,

It does notflhbv'v'ever, define the entering .vided' from each other by insulated joints,

UNITED STATES. PATENT OFFICE.

" LAURENCE A. HAWKINS, OF SCHENECTADY, NEW YORK, AS SIG-NO-R TOJGENERAL ELECTRICOOMPANY, A CORPORATION OF NEW YORK.

To all whom'itmay concern:

Be it known-"that I, Lannnncn A. HAW- KINS, a citizen of the United States, residing at Schenectady, in the county of Schenectady state of New "York, have invented certain new and useful Improvements in Bl p Signal Systems, of which the following-ism specification. I a

My invention relates to alternating ur-- rent si its ob ect'is to provide a continuous-rail system havin the same advantage with re-J spect togexac y defining the entering points of the block as the indnctivebond system.

Two types (if-systemsadapted-form on electric railways have 'e'en. proposed here. to ore. In one of these the blocks are dias in steam-road practice, and reactances or mductlve bonds are used to transmit the as to permit the railsto serve asret'urnfor' current of each block to its own track circuitzl i The other type of system may be applied tp the standard electric railway having both-rails condnctively' continuous for al curr'e'ntsi. The blocks are not separated from each} other b insulated joints, but othe'if'means are use for dividing the blocks from 0ther,-as, for instance, by employing-currents ofdifi'e'rent frequency for adjacenttbloek sections, sothat the current from onelhlock flowing into the next block cannot affect the relays of said next block. Such a system is disclosed in my prior application, Serial No. 329,347, filed August 6,

The cont-inuousrail system has the ad vantage of avolding the costof the inductive,

are exceedingly expensive, and also of offering'a better return for the power current.

points of the blocks with the exactness of the inductive bondsystem with its insulated joints. Ordinarily, this is'of no importance, since, as. pointed out in my rior appliczv. tion, by placin the signals a jacentto the transformers w ich supply the alternating currentto the track, and byausing tra s variation in the entering pomt of the block can be confined to a dorhparativelydw-feet:

BLOCK-SIGN AL SYSTEM.

I Specification of Letters Patent. ()(et. 19, 1909. Application filed April 23, 1909 3 Serial No. 191,707. I

-.o f the block should be exactly fixed. By

alisystems for electric railways, an'dmyp'resent invention- I am enabled to obtain this result wherever it is required, while preserving to a large extent the advantages of the continuous-rail system.

The system of my present invention, while employing insulated joints and reactances, is, a tine continuous-rail system, since the joints and-reactances do not confine the signal" currents in any Way; but, on the contrary, thegsignal currents can, and must, flow. past the, joints through the reactances in;. the normal operation of the system, so

' that'the'rails remain throughout their length .conducti'vely continuous for all currents.

The reactances are made exceedingly small, having an impedance which need not be greater. than that of 100 or 200 feet of rail; so'that the addition of the joints and reactances tothe track circuits simply have the effect of increasing the length of the track circuits by-IOO or 200 feet, or less. Since the reactances do not serve at all to confine the signal currents,- other means for separating. the block sections, such as the use of currents of different frequencies in adjacent tra'ck circuits, must be used. Since the "reactancesfare so small, their cost is very much less than the cost of the inductive bonds in the inductive bond system, but because of the special arrangement and location of the reactances in accordance with my invention, they serve to define the entering points of the blocks as effectively as reactances large enough to confine the signaling currents.

My invention will best be understood by- Figure 1 shows diagrammatically a block signal system arranged in accordance with .my invention; Fig. 2 shows diagrammaticallyf asuitable construction for the react- ;ance; and Fig. 3 shows my. invention applied to a modified form of system.-

- In Fig. 1, A represents the rails of an clec-,

tric railway which are conductively con-- tinnous .foraall currents throughout their length..."B and 13 represent alternating current generators of different frequencies fol snpplying current to the signal c rcuits.-

; I;- have indicated a three-wire;transmission"= In certain cases, however, as, for manager system and b the w-ire b serving-as 9 {the relays to prevent saturation by unbal common return for both frequencies. -U-,-C

Y and C represent transformers'hay'ing their -d carrying the relay contacts, a' winding (1? connected'to the'rails, and 'a second winding secondaries connected across the rails at iii-- tervals and their primaries connected to the transmission wires. Ad aceIit' transformers 'are'connected to transmission circuits of-different frequencies: Resistances care placed in series w th the secondaries of the transformers to limit the flow of current when the transformeris 'short-circuit'ed by acar-and alsojo'prevent saturation by an unbalanced flow of powercurrent. D, D,.,D and D represent. relays. which are jconnected in pairs across the' rails between adjacent sources- .The, relays are shown diagrammatically :as' of the well known induction type,.compris1ng a short circuited secondary d supplied independently of the rail circuits I with currentofaphase'.displaced from that in'thetrack winding d I have indicated transformers E'to E for supplying the sec- 50nd windingsof the relays. ,Ph'ase control j'ling'devices, such aslcondensers (5 may be employed, if necessary, to producea phase -.displacement'bz'et-weenthe currents in the two relay windings. q-Resistances 10 m be .advanceof, jeach source is the reactance F,

placed in'seri'es with the track windings of anced power-current. Adjacent to, and'in having itswindings inserted in the rails. Signals G,- G and G are placed at th'e react'ances, and each signal is controlled by thepair of relays nextbeyond theadjacent transformen -that is, signal G is controlled by relays-D and D .If the reactances F, F Y .and F were removed, the arrangement of v the systemwould be identical with that disclosedin my prior application, Serial No.

' 329,347, above referred to. A'car approaching the transformer G (the direction of trafficJbeing ,as-shown' by F the arrowl would gradually reduce the voltage supplied by this transformer to the track until when .the car had reachedya point near the. transformer, the track volt-age would be too low to maintainatherelay D energized, so that thht'rel'ay would openits contacts allowing signal G t'ogo to'stop position. ,The point reached by thejcar when the signal went to stop. would. 'vary slightly with different weather conditions; This variation, which.

can be made very small if the transformers have good'regulation, can be entirely elim-- the shunting point would be feet. reactance F is placed 50 feet, or a little less,

inated by the use .of thereactance F. For.

instance, if, under extreme weather condi tions, the relay D we're-shunted witha'car 50 feet and '100 feet, respectively from the transformer, then themaximum variation in- If the from. transformer C, and the -reactamce" of each of its windings is made equlvalent'to the impedance of a little more than 50 feet a of rail, then the' signal G will always go to stop the instant the front wheels of the car pass the rea'ctance, because, before the car reaches the insulated joints spanned by the reactance, there is between it. and the transformer an impedance equal to sllghtly more than thatfof 200 feet of rail, which, under "It would, of course, be possible to place fthe'reactance F at the secondary terminals of transformer C,'but by placing it in ad- -vance of the. transformer by a distance slightly. less than the minimum shunting,-

distance, the impedance of the rails between the transformers and reactances is utilized so that the reactance may be smaller.

the ratio between minimumv and maximum shuntmg distances is two to one, as m the case assumed above, the reactances so placed need be only slightly more thanhalf as large as would be necessary if they were placed at the transformer terminals. The reason that the rea ctan'ce may be of so small an amount is that the only tune it performs any useful function in the system is when a'ca'r isappro'aching it and is close to the transformer. Atthls time the transformer is delivering an abnormally large current, -wh1ch flows through the reactance and the wheels and axles of thecar, and this abnormally large current produces in the reactance a suflicientvoltage dropfor maintaining the relay. D energized, although the reactance' itselfis very small, since the voltage drop is the product of the current and the hu pedauce of the reactance.

\Vhen no car is approaching a reactance, the reactance has no function. The current from transformer C flows through the reactance F to energize relay D precisely as though the react-mm were absent. The only effect of the reactance with the block clearis to add an impedanoe to the track circuit between transformer and relay equivalent td lengthening the track circuit 50 or-100 feet that is, increasing its length, if the blocks are a mile long, by two to four per cent.

While it is not necessary that the reactance should have two windings, thetwo-winding" ar rangement is preferable, since both these windin may then be placed on a common I core, a idthe power current in the two windproduces opposing effects, so that the in only tendency to saturation by the power current is due to an unhaiancing of the flow in opposite rails." Fig. 2 shows diagrammatically the arrangement of the two windmgs f of the reactance F on a common core 7, which is provided with an airgap to prevent saturation by unbalanced power current. 1

In a prior application, Serial No.482,637, filed March 11, 1909, I have disclosed a modification'of the system of my earlier application, which modification consists in the .addition of a third'relay for each block; the third relay being placed near to and in advance of the transformer at the entrance of the block. The purpose of thismodification is to decrease the amount of current required for a given frequency, or to permit.

a decrease in the frequency with the same current consumption. Other things-being equal, the variation in the shunting point of the relay is: almost exactly proportional to its distance from the transformer which supplies it, so that by providing an extra relay near the transformer for fixing the entering point of the'block the transfor'mer may. have a lower voltage and poorer regulation than in the earlier form of the system,

circuitsmay be reduced.

In Fig. 3 I have shown my present invention applied to the form of system disclosed in application, Serial .No: 482,637. The relay I) is placed near to and in advance of the transformer C, and relays D and D are similarly .placed .with respect to transformers C and C respectively. The signals are placed near the relays D, D and D, and

or the frequency employed in the signal each signal is-controlled by its adjacent relay jointly-with the. pair. of relays nextbeyond the-adjacent ,transformerf-that is,

signalG, for instance, is controlled'by relays D, D and D When" my invention isapplied to this modification of a system, the

reactance F is placed at, or within the minimum shuntingdistance of, the track connections of relay D and acts to define exactly theshunting point of the relay D precisely as in Fig. I it acts todefine exactly-the shunting point of the relay'D. Comparing the arrangement of Fig. 3 with thatof Fig. 1, that of Fig. 3 requires an extra relay,but the size of the reactance may be even less than in'the arrangement of Fig. 1.

Referring again to Fig. 1, it 'will be seen that signal G goes to stop when acar passes reactance'F, and that signal G goesto stop when the car passes reactance S1 nal G does not, however, clear when signal asse There is thus an overlap in the system, the

amount of which is'not exactly fixed, butl which w-ill.vary somewhat-with weather connot resent.

1 e v .to sto but remains at stop until the car has transformer O a sufficient distance or the voltage of that transformer to use enough to cause relay D to closeits contacts;

additional protection, and the slight variation in its amount is ordinarily wholly immaterlal. If, however, 1t is desired to fix 'to fix the point reached by a car when signal G clears. In order to make the reactance F as small'as possible, itshould be placed at the distance from transformer D corresponding to the minimum distance at which under extreme weather conditions relay D would close its contacts, were the reactance y invention is applicable to other types of systems than that shown, and may be appliedin various combinations. Accordingly,

'I do not desire to limit myself to the particular construction and arrangement of parts here shown, but aim in the ap ended claims to cover all modifications whlch are within the spirit and scope of my invention! "I do not in this application make any claim to'a block signal system for railways having both, rails conductively continuous for all currents, in which adjacent sources-of current for the track circuits are of different character and the relays are selectively re sponsive to current of one character only,

nor do I make any claim to a system for such railways having the relays arranged in pairs between adjacent sources, since these matters form'the subject-matter of my prior applica-,

tion, Serial No. 329,347, above referred to.

definitely the point reached by the car when I What I claim as new and desire to secure by Letters Patent of'the United States, is,

1. In combination with an electric railuous for all currents,.sources of alternating current connected across the rails at intervals, each supplying current to track circuits on both sides of it, a pair of track relays between adjacent sources supplied with current'from the rails'and each responding to current from oneadjacent source only, a reactance having a winding inserted in a rail adj acent'to and in. advance of asource, and a signal-placed near said 'reactance and controlled by the pair of relays next "beyondsaid source,

2. In combination with an electric railway havin' both rails conductivelycontinuous for al currentsysouroes of alternating current connected across the railsjatjintervals,"each supplying current to track circuits on both sides of it, a pair of'track relays between adjacent sources supplied with current from the rails and each responding 1 way having .both rails conductively contina signalplaced near" saideactance and con-- trolled by the pairfof relays next, beyond 'said source,

'.I :Inf combination with electricrailway jhaving both rails vconductively QQntlll uous forfal-l currents, sources of. alternating current' .'connected across the rails at interval'sQj'each supplylng current to =trackc1r l'ays between adjacent sources" supplied with l cur int from"the-rails'and' each responding to current from",'one adjacent source To'hly," a 1 reactance inserted in the rails adjacent to ,anddngadvance of a sourcegfa' relay connect ed across the r-ails between"saidQreactance w "and said source, and a ".slgnal placed (near said reactance' and controlled jointly'by the fla stementioned relay and :the Pai of relays next beyond said source; 1 1, Q i 4. In combinat on jgwith'r an electricjraiL .way ha'v ing both. rails:-conductivelyfcontim uo'us for-all currents, sources Jot-alternating lay; connected acrossthe railsibet-ween said reactance' and said; sourcey'f and alsignah placed near' said '-=rea ctance" and controlled jointlyhy vthe last-mentioned relay and the; .'pair ofrelay's' next beyond s'aidfsource 5. .In combination with an electric rails way'jhavin both rails conductively GQIltlllj. {nous for al currents, sources of alternating current connected across the rails at inter-p ra ls, each supplyingcurrent to track cir-' cuits'fon both sides of it and thecurrents" from adj acent. sources differingin charac-. ter, Itrackf. 'rela ys connected across the rails 'in pairsbetween adjacent sources, each relay beingresponsive onlyjtocurr'ent of the charsource, signals placed neafsa d sources each c'ontrolled'by the pair of relays next beyond the adjacent source, and -a- ,reactance having a winding insertedflinxal rail near a source ,whereby ithe passage of'a car over said rev -.-.actanc'e produces a sudden var ation o fvoljtagein the track circuit on the other side of saidsourcah .x

.t ro'l circuits. l I v 8; In a block-signal system, in combination. I with the -signals and control circuitsthcre- I 6. In combination with an electric railway having both rails c'onducti'vely' continuous for all currents,. sourc"es of alternating c urrent connected .acros s'fthe rails at intervals,

.each supplying current to track circuits on both sidesof it. and'the currents from adja cent sources'di'flering injcharacter, track relays connected across the rails in' airs-between adjacentsources each relay eing rel spon'srve only to current of the character "supplied; to the rails'lby one adjacent source,

signals). placed near said sources feach controlled by the pair ofrelaysj next beyond th .adjajcentjsource, and a reactan'ce comprising two windings: on- "one core; inserted respectively in opposite rails adjacent to a source whereby the passage of a carover said'reactl anceproduces a, sudden variati'oncf .yoltage in 'the track circuit on the other side of said source j a 7'.3In a block signal-system, in colnbination .avith the'signals and; control CllCllltS there for, a-source of alternating current connected v across therails; a track'relay at a distance from said source energized. by current therefrom suppl ed through the rails, a roactance havinga w nding inserted in the track circult' at a point between the source and the relay, and-"a second? relay connected across .85

I, th'eflfails near the reactance between the l e .;actance and -the source andfenergized with current, from said source, the contacts of the two relays being connected in different confor, a source of alternating current connected across the rails, a track relay at a distanc;

from. the source energized by current there point between the, source and the relay, and

the reactance -between the reactance and the p source and energized with current from said ,act'er supplied to the; rails by one adjacent source,*, the contacts 'Of the two relays being connected in difl'erent control circuits.

a second relay connected across the rails near 

